On the topic of regional differences in the meaning of "frown":
As per Merriam Webster (online):
\ ˈfrau̇n \
frowned; frowning; frowns
Definition of frown
(Entry 1 of 2)
1 : to contract the brow in displeasure or concentration frowned in anger
2 : to give evidence of displeasure or disapproval by or as if by facial expression critics frown on the idea
: to show displeasure with or disapproval of especially by facial expression
I will be neither frowned nor ridiculed into error— Noah Webster
As per Lexico (online):
- 1Furrow one's brows in an expression indicating disapproval, displeasure, or concentration.
- ‘he frowned as he reread the letter’
‘promiscuity was frowned upon’
Based on the above, I don't see a difference between AE and BE.